Generally aqueous resin compositions such as paints, coatings, sealers, caulks and fillers are modified for improved elongation by adding a plasticizer to the composition or by changing the characteristics of the resin itself, for example lowering the glass transition temperature (Tg) of the resin. Changes such as these may greatly impact the overall performance of the resin composition.
Fibers and fillers have been used in the past to reinforce resin compositions, but reinforcement, while increasing the tensile strength and modulus, causes a reduction in the elongation of the composition.
Examples of teachings of reinforced resin compositions include U.S. Pat. Nos. 4,514,541, which teaches reinforcement of elastomers by incorporation of p-aramid short fiber into the elastomer composition; 5,331,053, which teaches the use of fibrids for reinforcement of elastomers; and 4,460,737, which teaches the use of polyolefine fibers in polyurethane sealers.
The present invention relates to the use of a special organic polymeric material in resin compositions. The polymeric material is a fibrid. A fibrid is not a fiber. A fibrid is an organic particulate that is film-like and has a moderate to relative high surface area. Fibrids are formed by extruding or spinning a solution of the polymer into a non-solvent (for the polymer) coagulation bath while the bath is under vigorous agitation. This non-solvent needs to be miscible with the solvent of the polymer solution.
Fibrids were first introduced in U.S. Pat. No. 2,999,788 to Morgan. Morgan taught methods for making fibrids and a variety of applications. But unlike the present invention Morgan did not teach a fibrid dispersion, that is a combination of fibrids and filler in a water dispersion. Morgan listed the use of fibrids as materials for reinforcing resins and resin compositions, but Morgan did not teach how to use fibrids as a means to increase the elongation of a resin composition.
The present invention provides an aqueous dispersion of fibrids stabilized in water by a combination of an inorganic particulate filler, a coupling agent and a surfactant. This dispersion may then be incorporated into a resin composition to form a mixture. Cured films formed from this mixture show elongations of 2 to 3 times those of cured films formed from the resin composition alone. While at the same time, the strength of cured films formed from this mixture are about equal to those of cured films formed from the resin composition alone.
An object of the present invention is to provide cured films having greater elongation and a more elastic behavior. Another object of the present invention is to provide latitude in formulation resin compositions so that equal elongation may be achieved using stiffer or less costly ingredients.